Portable spray apparatus are used in fruit orchards, vineyards and vegetable farms for applying a plant protective medium. A plant protective medium is placed in the supply vessel of the spray apparatus. The blower unit generates a blower airflow with which the medium is drawn out and directed to the plant matter to be treated.
Depending upon the application, it can be required to deliver a liquid spray or a solid dust medium. In order to satisfy both requirements with the same basic apparatus, adaptive work is needed. During spray operation, a liquid spray medium is stored in the supply vessel. This liquid spray medium is drawn off from the supply vessel via a liquid channel and, for example, is introduced into the blower airflow by means of a pressure pump. The liquid channel includes a flow line and a return line in combination with the pressure pump. These lines communicate flow conductively with the interior space of the supply vessel. This arrangement is designed for the movement of liquid spray medium.
In dusting operation, a powdered or granulated dust medium is discharged and the liquid channel and the pressure pump are not suitable to convey this medium. Rather, a metering device is used which draws the dust medium from the interior space of the supply vessel. The dust medium is conducted via a solids channel into the blower airflow. This solids channel is adapted to the material characteristics of the powder or granulate.
Insofar as the same basic apparatus is to be utilized for the selective operation with spray medium and solid dust medium, individual assemblies must be exchanged with these assemblies being adapted especially to the liquid or solids to be applied. Complex conversion measures are required. The particular assembly not used must then be separately stored and can become lost.